1. Field of the Invention
This invention relates to a method of pre-heating boiler feed water, in which effective use is made of a low temperature range of heat generated from petroleum refineries without involving equipment corrosion.
2. Prior Art
Heretofore, such vapors of hydrocarbon fractions boiling in a range of gasoline as may be obtained by straight-run or catalytic cracking of crude oil normally have a temperature ranging from 90.degree. C. to 150.degree. C. Since recovery of heat from such low temperature hydrocarbon vapors is difficult and such vapors are required to be liquefied by cooling, there have generally been used heat-exchangers or condensers for cooling and liquefying the vapors with use of sea water. In such instance, various copper alloys such as aluminum-brass, naval-brass and the like have been employed for the condenser tubing from the standpoint of necessity for preventing the tubing from corrosion in contact with sea water. Most heat generated in the equipment has been simply discarded.
On the other hand, boiler feed water has been generally provided by filtering water for industrial use, pre-heating or heating pure water which has been de-salinated and de-ionized through filtration, then introducing the same into a deaerating vessel at a temperature of about 100.degree. to 130.degree. C. to remove air and oxygen dissolved in the pure water prior to feeding the boiler. Pre-heating has been effected usually with use of hot steam. However, since intake water is near room temperature or much lower temperature during the winter season, a great deal of heat is required to pre-heat the water to a desired level of temperature.